Translating apparatus



Aug; 27, 1935. '1'. H. LONG I 2,012,573

Trumsm'rme APPARATUS Filed D66. l5, 1931 WITNESSES. INVENTOR llnu '772077205 H Long.

ATTORNEY Patented Aug. 2 7, 1935 PATENT OFFICE I mnsm'rmo msas'rusThomas 1!. Long, Irwin; Pa a-ignor to Westingacturlng house Electric &Mann! corporation 0! Pennsylvania Company, a

Application December 15, 1931, Serial No. 581,152-

18 Claims. (01. 171-312) ations in the source of illumination wherebythe My invention relates to translating apparatus and has particularrelation to apparatus of the type incorporating electric dischargedevices.

It is an object of my invention to provide, tor a translating system ofthe type incorporating a plurallectrode ,electric-discharge device, a

contrivan e for compensating for the variations 1 introduced in theresponse of the system by the effects of external physical disturbances.

Another object of my invention is to provide a translating system oi thetype incorporating electric-discharge devices that shall have a uniformresponse regardless of the normally vitiating disturbances arising inthe region wherein the system is disposed.

Still another object of my invention is to provide an energy translatingsystem of the type incorporating electric-discharge devices that shallrespond uniformly regardless of the normally vi tiating disturbancesarising by reason of variations in the systems with which the apparatusis associated.

A further object of my invention is to provide a photo-sensitive relayoi the type incorporating an electroionic or an electronic-amplifyingdevice that shall always haves predetermined response when influenced byradiations of predetermined characteristics'regardless oi the influenceoi the physical properties of the environment'of therelay.

A still further object oi my invention is to provide a relay oi. thetype incorporating a photosensitive trigger and an electrolonic or anelectronic amplifying device for the trigger that shall have apredetermined response for predetermined illumination impinging on thetrigger regardless of the variations in the elements associated with therelay and cooperating therewith.

A specific object oimy invention is to provide for an energy translatingsystem, a contrivance for compensating for the eflfects of variations inphoto-sensitive trigger oi! the relay is excited.

More concisely stated, it is an object o! my invention to provide anenergytranslating systemoiatypethatshallbeparticuiarlyapplimble insituations where uniform response is required regardless of thecharacteristics oi the apparatus associated with the energy translatingsys-' tem and of the environment of the translating system.

According to my invention, I provide an energy translating systemincorporating a balanced network having input and output terminals. Thebalanced network' may be of the Wheatstone bridgetype and its armsshould be of a character suitable for the purposes for which the networkis utilized.

Normally, the input circuit is connected to two conjugate terminals ofthe network and the output circuit is connected to two other conjugateterminals. The input terminals are connected to a power supply sourceand when the network is incorporated in the translating system for thepurpose of compensating ior the eilects oi variations in thepower-supply source, that feeds the system, the input terminals of thenetwork are connected to the power-supply source that feeds thetranslating system. Moreover, ii the net-' work is to providecompensation for variations in the power-supply source,the arms of thenetwork that effect the necessary compensation are of a type responsiveto voltage or current variations.

On the other hand, it the network'is to compensate tor the effects 01'ambient temperature put terminals thereof are connected preferably to anindependent power-supply source'and the arms of the network that eii'ectcompensation are of a character responsive to ambient temperature orhumidity variations.

The output terminals of the network, whether it is utilized forcompensating for voltage variations, temperature, humidity variations orother types of variations are coupled to the energy translating systemin such manner as to provide the necessary compensation. It isunderstood, of course, that the coupling may be a direct connection, anelectrostatic connection or an electromagnetic connection depending onthe contingency of the situation. In many instances I have found in thepractice of my invention thatan electromagnetic connection yields rathersatisfactory results, since the electric discharge devices that areutilized in the translating systems of the type in which I amparticularly interested respond to voltage variations rather than tocurrent variations and by utilizing the proper transformers, I 1

can attain the necessary voltage without considerable loss of power inthe network.

As has been suggested hereinabove, in the preferred practice of myinvention, the network is commonlya Wheatstone bridge. When the networkis utilized for compensating for variations in the output of the sourcesupplying energy for the operation of the energy translating device, twoopposite arms or the bridge are of a type having a substantial voltagecoefficient of resistance. The other arms or the bridge are of a typehaving an inappreciable voltage coeiilcient of resistance.

It is of course understood that essentially only a difierence in thevoltage coeflicients of resistance of the two sets of opposed arms isnecessary. Hence one set may have a positive voltage coefli= cient ofresistance and the other set a negative voltage coeiiicient ofresistance, or one coefficient may be high while the other is low.

The output of the bridge is inductively coupled to one or more of theinput circuits of the electric discharge devices incorporated in the energy translating system.

For predetermined output of the power sup ply system the networlr is soadjusted that it has zero output or possibly a predetermined output. Avariation in output of the power system produces a variation in. theinput of the network and consequent variation in output the .uEb'WGlk,The change is im, 'essecl suitably on oneor iriost of the controlcircuits of the electric devices. effect of the irr resscd s on theelectric discharge devices is to compensate lor the effects ofvariations in the supply system on the output or. the elecl devices.

"lotecl normally the e power supply source is to s impressed between theprinci le electric discharge device or e s stein, a d the con; 1 also,to ch nge e pots electrodes.

- n these changes co s corresconduit! changes iritrodu t... ww

- tive trigger, the source or illumination whereby the trigger isenergized is normally excited from the power source whereby thetranslating system is energized. Conse uuently, a variation in the powersource not only affects those potentials associated with the elec== triodischarge device and with the photo-sensi-= ive trigger, but alsoaflects the source of illumina= tion. By properly coupling a suitablenetwork provided in accordance with my invention to energy translatingsystem of this type, not only are the effects of Voltage variations on.the elec trio discharge devices compensated but the effects .anappreciable temperature coefiicient of resistance, while the other armsare constructed of a metal having substantially a zero temperature coefiicient of resistance. Specifically, the former set of arms might beiron, while the latter set of arms might be Advance. It is to be noted,moreover that in general, for purposes of temperature compensation, thegroups of arms need only be of such character that they are eachcomposed of metals that differ appreciably in the temperaturecoefiicient of resistance of the individual elements; that is to say,the set of arms having the lower temperature coefficient of re sistanceneed not necessarily have a zero temperature coefficient of resistancebut may have a negative temperature coefiicient of resistance or even alow positive temperature coeificient of resistance.

The novel features that I consider characteristic or" my invention areset forth with particularity in the appended claims. The inventionitself, howevenlooth as to its organization and its method of operation,together with additional objects and advantages thereof, will best beunderstood from following description of specific embodiments when inconnection with the accompanying drawing, which:

Figure .l is diagrammatic View showing an embodiment of my invention, asit is implied to the compensation of variations in the source wherebypower is supplied to energy translating system.

. is a diagrammatic v odiinvention as,

a diagrammatic vie vention as it ut" ii the ambient h ratus shown in l,primary ource (not sh one se s ill the l;

1, other cui'y pool ole .(l may tube without eatures o.. invention. thebalances network 2i, u e on, are connected. across annals the powersupply 3 :imary 5i and ate terminals 23 of the network variableresistance oi suitable charhave subual in m nitude. These resistors Theother e ro voltage coefdcients.

- s nice at a given voltage.

desired that the network iii shall be balanced under normal conditions,the resistors should be of such character that, when conditions arenormal, they have the same resistonce as resistors 29. Under suchconditions, the resistances of. all sides of .the network will beidentical.

It will be noted. that since tungsten and carbon have voltagecoeflicients of resistance of opll utilized in posite sign that it maybe desirable to use a network in which the opposite arms arerespectively tungsten and carbon.

The output leads of the network are fed from two conjugate terminals 3|thereof'and are connected through the primaries 33 and 35 of aplurality. of transformers 51 and 35, the secondaries 4| and 43 of whichare in turn connected between the control electrode 45 and the principalelectrodes 1 and 5 of the electric discharge device II.

In the system of the type shown in Fig. l, the triggering device 41 isof thephoto-sensitive type and comprises an ordinary photo cellconnected between the control electrode 45 of the tube I I and thesecondary 45 of the compensating transformer 35. Potential is applied tothe cell 41 from a potentiometer 49 that is, in turn, energized from asuitable section of windings 5| of the secondary 5 ofv the power supplytransformer I. The lower tap 53 of the potentiometer 49 is connected tothe cathode 9' of the electric discharge device ll through the impedanceI1.

An impedance 55 of proper magnitude is also connected between thecontrol electrode 45 and one terminal of the secondary 4| of thecompensating transformer 51 that is disposed in the control circuit 35associated with the anode 1 of the electric discharge device H.

The photo-sensitive device 41 is energized from a suitable source ofillumination 51 that is supplied with power from'a section 55 of thesecondary 5 of the power supply transformer i.

The network 2| is so adjusted that'for a predetermined output of thepower source I, the resistances 29 are equal in magnitude to theresistances 21. The output of the network is theri zero and the electricdischarge device I I is not effected thereby. When the output of thepower source changes, the resistances of the lamp filament arms arechanged and the balance of the bridge 2| is disturbed. In such a case acurrent having a polarity and a magnitude determined by the polarity andmagnitude of the change in the power supply transformer I, flows throughthe primaries "and 35 of the compensating transformers 51 and 35,respectively, and corresponding potentials are impressed on thecontrolcircuits l5 and 5| of the" electric discharge device ll.

The character of the compensating voltage which need be supplied by thebalanced network 2 I is dependent on the character of thephoto-sensitive device 41 and of the electric-discharge device i Iutilized in the system. If the electric-discharge device is of thegrid-glow type, as is shown in Fig. 1, the variation in the output ofthe primary 5. since it effects a variation between the controlelectrode 45 and the principal electrodes 1 and l of theelectric-discharge device II, has the effect of changing the breakdowncharacteristic of the system. The electromotive force impressed betweenthe cathode 5 and the anode 1 of the electrio-discharge device of thegrid-glow type is normally given such a factor of safety that it is notaffected.

For example, if the output of the power source should be decreased, thepotential between the cathode 5 and the anode 1 of theelectric-discharge device would be decreased with substantially noeffect. If at the same time a photosensitive device 41 of the highvacuum type is utilized in the system, the .current through thephotosensitive device remains constant in spite of the decrease ofelectromotive force impressed thereon and consequently the drop ofpotential between the anode 1 and the control electrode 45 remainsconstant. As a result of this situation,

the potential drop between the cathode 5 and the control electrode 45 isdecreased and less negative charge is required to be supplied by thecell 41 to the control electrode 45 of the electricdischarge device IIto prevent the device from becoming energized than was required beforethe variation in the power output of the primary I took place. That isto say, the electric-discharge device now becomes energized for a lowerflux of illumination impinging on the photo-sensitive trigger 41 than itdid before the change took place.

In such a system the properties of the elements of the balanced network21 are such that the electromotive force induced between the controlelectrode 45 and the anode 1 of the electric-discharge device II has theeffect of raising the voltage of the control electrode 45 relative tothe cathode 9 and of thus reverting the system to its originalcondition.

In the system of the type incorporating the high vacuum photo-sensitivecell, it will be noted that compensation of the system for the effectsof the decrease of the illumination impinging on the photo-sensitivecell is not possible by the utilization of the lower compensatingtransformer 39. This transformer would have only the effect of raisingthe electromotive force impressed on the cell 41, and, since the cell,is of v the high vacuum type and is normally operated in its saturationregion, the increase in the electromotive force applied to the cellwould have no notable results. However, it is possible by properlydesigning the upper compensating. transformer 31, for example, or byutilizing two compensating transformers to affect the circuit 35associated-with the control electrode 45 and the anode 1 to compensatefor the variations in the source 51 that provides the illumination forexciting the photo-sensitive cell 41.

The application of my invention to a system incorporating a high vacuumphoto-sensitive cell in which it is necessary to compensateforvariations in the illumination-produced by variations in the powersource should be apparent to one' skilled in the art and need hardly bedescribed herein. It need only be noted that if a decrease in theillumination takes place, for example, by-reason of a decrease in theoutput of the power source, fewer negative charges are supplied to theelectric-discharge device ll than were supplied before the change tookplace and the potential of the control electrode 45 relative to thecathode 9 need, therefore, be decreased to compensate for the change. Acorresponding situation arises when the power output of the power supplysource is increased. When the photo-sensitive device 41 utilized in thesystem is of the gas filled type, since the effect of the variations inthe output of the power supply system is to change the electromotiveforce impressed, across the photo-sensitive device, a consequent changein the current output of the photo-sensitive device takes place and thepotential of the anode 1 relative to the control electrode 45 of theelectric discharge device If is changed, as well as the potential of thecathode 5 relative to the control electrode. In such a case, it will benoted, that while the effects introduced by the compensatingtransformers must be of the same polarity as for the systemincorporating the vacuum cell, the magnitude of the changes are somewhatdifferent and as a result the compensating system must be designed 75 Iof secondaries 85-and 81.,- 7 however, that the windings to suit theparticular translating system with which it is to be utilized.

It is to be remembered also that while the potential of the controlelectrode 45 of the electrio-discharge device ll relative to the cathode9, is changed by the compensating efiect, the potential of the anode 63,of the photo-sensitive device 51, is also changed relative to thecathode 65. The character of the compensating network 2i and of thetransformers 31 and 39 associated therewith should preferably be of atype such that the anode 63 is raised to the same potential relative tothe cathode 65 that it had before the change in the output in the powersupply system took place. I may further say that in the systemincorporating the gas filled photo-sensitive device, the compensationfor variations in the source 51. of illumination may take place throughthe compensating transformer 39 associated with the circuit 6! of theenergy translating network in which the photosensitive device 4! isconnected. This situation arises by reason of the fact that the outputcurrent of a gas filled photo-sensitive device may be controlled bycontrolling the electromotive force impressed between its terminals.

It will be noted that while I have shown my invention as applied to aparticular circuit, it is equally as well applicable to circuits ofothertypes. The circuit of the type shown in Figure 1, is commonly known asan inverse circuit; that is to say, it is a circuit in which the effectproduced on the electric-discharge device is in inverse relation to thestate of excitation of the photo-sensitive device. If thephoto-sensitive device 41 is highly excited, the electric-dischargedevice II is deenergized, while, if the photosensitive device is in astate of low enough excitation, the electric-discharge device isenergized.

The apparatus of the type shown in Fig. 2 incorporates a hot cathodeelectric-discharge 'device 61 in place of the cold cathodeelectric-discharge device ll utilized in apparatus of the type shown inFig. 1. The electric-discharge device 61, shown in this view, may be ofthe gas filled or high vacuum type and comprises a cathode 69 heatedfrom a suitable section II of the secondary 5 of the power supplytransformer l, a control electrode 13 and an anode I5.

The output of the electric-discharge device 61 feeds through a meter 11or a load of suitable character depending on the use to which the systemis put. The photo-sensitive trigger 41 of the system is connected to anindependent section of windings 19 of the secondary 5 of the powersupply transformer I and the electromotive force impressed thereon isdependent only on the condition of the primary 3 of the transformer. Thecompensating system is of the same character as that shown in Fig. 1with the exception that the compensating transformer 8| in the presentinstance has a single primary 83 and a plurality It is to be noted,

85 and 81 should be of such character as to provide the properelectromotive force for compensating purposes, and, by reason of thefact that the electromotive force impressed in the output of thecompensating network is ordinarily rather small and the electromotiveforce required for compensation is ordinarily considerable, I have'foundthat the numberof turns of the secondaries 85 and 81 (and particularlyof the secondary 85 whereby compensation for varying the of thesecondariesv sensitivity of the cell 41 'is provided) should be Theresponse of the system of the type described in Fig. 2 is the same asthe response of the system of the type described. in Fig. 1. In analogywith the hereinabove set forth explanation, the two compensatingsecondaries 85 and 81 incorporated in the system may be utilized,

.respectively, for compensating for the effects .of variations in theillumination impinging on 4 shown in Fig. 2. As in apparatus of the typeshown in Fig. 2, the output current of the electric discharge device 67feeds through a meter 11 or a load of suitable character and iscontrolled by the response of a photo-sensitive device 41 to one or moresources of illumination (not shown). The power necessary for theoperation of the system is provided by a suitable transformer 19 througha potentiometer 9| of proper character.

The compensating network 92 comprising a Wheatstone bridge, the pairs 93and 95 of opposite arms of which are composed of metals between whichthere is a substantial difference in temperature coefficient ofresistance, is fed from an independent power supply transformer 91through a potentiometer 99 of proper character. As has been explainedhereinabove, two arms 93 of the bridge may be of advance, which hassubstantially zero temperature coefficient of resistance, while theother two arms 95 of the bridge may be composed of iron which has asubstantial temperature coeflicient of resistance.

The output of the netwo-rk'92 isfed into the input circuit of theelectric-discharge device 81, one output lead IUI being connected to thecontrol electrode 13 of the electric discharge device 61 and the, otheroutput lead l0l being connected to the potentiometer 9| whereby power issupplied to the electric-discharge device. The balanced network 92 maybe so adjusted that normally a predetermined biasing electromotive forceis applied to the control electrode 13 of the electric-discharge device61 through the output leads "ll of the network. A change in the ambienttemperature produces a change in the resistance in the arms 95 of thebridge and a consequent shift in the potential of the output terminalsI03 of the network 92. The shift in the potential is so impressedbetween the control electrode 13 and the cathode 69 of theelectric-discharge device 61 that the necessary compensation for ambienttemperature variations takes place.

It shouldbe kept in mind that the effects of ambient temperaturevariations on the electricgreater in number of turns than of the primarydischarge device and on the photo-sensitive device utilized intranslating systems have been rather aggravating in the past. The outputof the electric-discharge device is apparently rather sensitive totemperature variations and thedevelopments which gave rise to thepresent inmethod taking care of the vitlating influences on the output01 the electric-discharge device of the ambient temperature variations.By utilizing the balanced network as described herein-.

above, I have found that the deleterious effects of temperaturevariations are substantially eliminated and that the system has uniformresponse regardless ct temperature variations in its neighborhood. V

While I have'found that for the practical purposes to which I haveapplied translating apparatus incorporating electric discharge devices,the elects introduced by variations of other types than temperature.variations and voltage variations are substantially negligible, it ishighly con-' ceivable that in certain types of apparatus the eifects ofthese variations might become of some importance. It will be observedthat my inven-- tlon is applicable to compensation of ambient humidityvariations and changes of other types produced in the environment of thetranslating apparatus. Systems-in which other variations in theenvironment of the translating apparatus than temperature variations orvariations in the power supplied for energizing the translating systemare compensated, are therefore, equivalents which lie within the scopeof my invention.

Although I have shown and described certain specific embodiments of myinvention, I am fully aware that many modifications thereof are poseslble. My invention, therefore, is not to here-- strictedexcept insofarasis necessitated by the priorartandbythespiritoftheappendedclaims.

I claim as my invention:

1. In a translating systemof the type including an electric dischargedevice having input and output terminals, power supply means connectedto said output terminals, and means responsive to ambient temperaturevariations coupled to said input terminals of said electric dischargedevice to compensate. for the effects of ambient 7 temperaturevariations thereon.

2. In a translating system of the type including an electric dischargedevice incorporating a control electrode and a plurality of principalelectrodes, a network, including a plurality of symmetrically relatedarms having a substantial temperature coeilicient of resistance and a'plurality of symmetrically related arms having a small temperaturecoeiiicient of resistance, said network having input and outputterminals, power supply means connected to said input terminals, andmeans for coupling said outputtertrlcdischargedevicirtdcompensatefortheeb" fects of ambienttemperature variations thereon.

4. The combinationwith anelectric discharge device of a network havinginput and output terminals, power supply means coupled to said inputterminals, means to respond to ambient temperature variations to varythe voltage impressedacroassaidoutputterminalsandmeansforcouplingsaidelectricdbchsrgedevicetosaidoutputaora's'rs terminals to compensate for the eifect of ambient temperaturevariations thereon.

5. The combination with a network of the type having input and outputterminals including a plurality of groups of symmetrically related arms,6 the temperature coemcients of resistance of the elements of one groupbeing substantially different from those of elements of another group,and means for impressing an electromotive force across said inputterminals, of an electric disl0 charge device and means for couplingsaid output terminals to said electric discharge device to compensatefor the effect of ambient temperature variations thereon.

6. A translating system comprising an electric 1 I discharge devicehaving a controlelectrode and a plurality of principal electrodes,circuits associated with said principal electrodes and with said controlelectrode, power supply means for energizing said electric dischargedevice coupled 2 to the circuits associated with the electrodes of saiddevice, a circuit having input and output terminals and incorporating aplurality of symmetrically related conductive arms, certain of said armshaving an inappreciable voltage coemcient of resistance and certainothers of said arms having an appreciable voltage coeflicient ofresistance, means for coupling said input terminalsto said power-supplymeans and means for so coupling said output terminals to at least one ofthe circuits associated with said control electrode and said principalelectrodes of said electric discharge device as to compensate for theeffects of variations in the voltage oi. said power supply means on theresponse of said electric discharge device.

7'. A translating system comprising an electric discharge device havinga control electrode and a plurality of principal electrodes, a circuitassociated with said p ipal electrodes, a plural- 40 ity of circuitsassocia with said control electrode and'said principal electrodes,photosensitive means, of the type having a saturation characteristiccoupled to one of the circuits associated with said control electrodeand one of said principal electrodes, power supply means coupled to thecircuit associated with said principal electrodes, the electromotiveforce supplied to the circuit coupled to said photosensitive means beingof such magnitude that said photosensitive means is normally operated inits saturation region, a circuit having output terminals and havinginput terminals coupled to said power supply means, said circuitincorporating means.

responsive to theelectromotive force impressed thereon and means forcoupling the output terminals of said balanced circuit to the circuitcoupled to said photosensitive device to vary the electromotive forceimpressed on said lastnamed circuit and thus to compensate for the 60eflects, on the condition of said circuit associated with the principalelectrodes of said electric discharge device, of variations in saidpower supplyvoltage.

a 8. A translating system comprising an electric as discharge devicehaving an output circuit and a plurality of input circuits, power supplymeans coupled to said output circuit to apply an electromotive force tosaid output circuit and said input circuits, photosensitive meansconnected in one of said input circuits, said photosensitive means beingof a type having a response that is a function of the electromotiveforce impressed thereon, and means coupled to another of said inputcircuits and to said power supply means 76 for compensating for theeffects on said output circuit of variations in said power supplyvoltage.

9. A translating system comprising an electricdischarge device having acontrol electrode and a plurality of principal electrodes, means forimpressing potentials between said control electrode and said principalelectrodes and between said principal electrodes, a network including aplurality of arms having substantially difierent coefiicients ofresistance, said network having input and output terminals embracingdifferent arms thereof, power-supply means connected to said inputterminals and means for so coupling said output terminals between thecontrol electrode and the principal electrodes of said electricdischarge device that variations in the operating characteristics ofsaid electric discharge device that are produced by conditions tendingto produce a change in the resistances of certain of said arms areneutralized by the additional potentials impressed between said controlelectrodes and said principal electrodes from said network.

10. A translating system comprising an electric discharge device havinga control electrode and a plurality of principal electrodes, means forimpressing potentials between said control electrode and said principalelectrodes and between said principal electrodes, a network including aplu= rality of arms having substantially different voltage coeflicientsof resistance, said network hav-= ing input and output terminalsembracing different arms thereof, power-supply means connected to saidoutput terminals and means for so coupling said output terminals betweenthe control electrode and the principal electrodes of said electricdischarge device that variations in the operating characteristics ofsaid electric discharge that are introduced by variations in thepotential supplied by said means for impressing potentials between theelectrodes of said electric discharge device are neutralized by theadditional potentials impressed between said control electrodes and saidprincipal electrodes from said network.

11. A translating system comprising an electrical discharge devicehaving a cathode, an anode and a control electrode, a voltage sourceconnected to cause current flow between said anode and cathode, anetwork comprisinga bridge cir cuit, the opposite sides of said bridgebeing resistances of similar temperature coeificients but thetemperature coeflicients of adjacent sides of said bridge beingdissimilar to each other, connections from a pair of diagonally oppositejunctions of said bridge circuit to said voltage source and connectionsfrom the other pair of diagonally opposite corners of said bridge toimpress a voltage tending tomake said control electrode less positiverelative to said cathode whenever said voltage source makes said anodemore positive relative to said cathode.

12. A translating system comprising an electric discharge device havinga control electrode and a plurality oi principal electrodes; a circuitassociated with said principal electrodes, a plurality of circuitsassociated with said control elec-- trode and said principal electrodes,photosensitive means, of the type having a saturation characteristiccoupled to one of the circuits associated with said controlelectrode andone of said principal electrodes, power supply means coupled to thecircuit associated with said electric discharge device, the resultantelectromotive force supplied to the circuit coupled to saidphotosensitive means being of such magnitude that said photosensitivemeans is normally operated in its saturation region, means to beenergized from said power supply means for energizing saidphotosensitive device, a network having output terminals and inputterminals coupled to said power supply means, said network incorporatingmeans responsive to variation in the electromotive force impressedthereon, and means for coupling the output terminals of said network tothe circuit coupled to said photosensitive device to vary theelectromotive force impressed on said last-named circuit in such a senseas to compensate for the effects, on the condition of said circuitassociated with the principal electrodes of said electric dischargedevice and on said energizing means for said photosensitive device, ofvariations in said power supply voltage.

13. A translating system comprising an electric discharge device havinga control electrode and a plurality of principal electrodes, circuitsassociated with said principal electrodes and with said controlelectrode said principal electrodes, photosensitive means, of the typehaving a saturation characteristic, coupled to a circuit associated withsaid control electrode and one of said principal electrodes, powersupply means coupled to a circuit associated with said principalelectrodes, the electromotive force supplied to the circuit coupled tosaid photosensitive means being of such magnitude that saidphotosensitive means is normally operated in its saturation region, acircuit having output terminals and having input terminals coupled tosaid power supply means, said circuit incorporating means responsive tothe electromotive force impressed thereon and means for coupling theoutput terminals of said circuit to the circuit coupled to saidphotosensitive device to vary the electromotive force impressed on saidlast-named circuit in such a sense as to neutralize the efl'ects, on thecondition of said circuit associated with the principal electrodes ofsaid electric discharge device, of variations in said power supplyvoltage.

14. A translating system comprising an electric discharge device havinga control electrode and a plurality of principal electrodes, circuitsassociated with said principal electrodes and with said controlelectrode and said principal elec-- trodes, photosensitive means coupledto a circuit associated with said control electrode and one or saidprincipal electrodes, power supply means coupled to circuit associatedwith 'said principal electrodes a circuit having output terminals andhaving input terminals coupled to said power supply means, said circuitincorporating means responsive to the electromotive force impressedthereon and means for coupling the output terminals of said circuit tothe circuit coupled to said photosensitive device to vary theelectromotive force impressed on said last-named circuit in such a senseas to neutralize the eifects,

on the condition of said circuit associated with I the principalelectrodes of said electric discharge device, of variations in. saidpower supply voltage.

15. The combination with an electric discharge device of a networkhaving input and output terminals, power supply'means coupled to saidinput device and a photosensitive devicetor controlling said electricdischarge device of a network having input and output terminals, powersupply I means coupled to said input terminals, means to respond toambient temperature variations to vary the voltage impressed across saidoutput terminals and means for coupling said electric discharge deviceto said output terminals to com-- pensate for the efiect of ambienttemperature 10 variations thereon.

20 said control electrode and said principal electrodes, photosensitivemeans coupled to a circuit associated with said control electrode andone of said principal electrodes, power supply means coupled to acircuit associated with said principal electrodes, a source of radiantenergy {or exciting said photo-sensitive device, said source beingenergized from said power supply means, a circuit having outputterminals and having input terminals coupled to said power supply means,said circuit incorporating means responsive to the electromotive forceimpressed thereon and means for coupling the output terminals of saidcircuit to the circuit coupled to said photosensitive device to vary theelectromotive force impressed on said last-named circuit in such a senseas to neutralize the eflects, on the condition of said circuitassociated with the principal electrodes of said electric dischargedevice, of variations in said power supply voltage.

' THOMAS H. LONG.

